The specific aims of this research are to isolate and identify the specific eye screening pigments found in Drosophila acanthoptera, and to determine how the various pteridine and ommochrome biosynthetic pathways interact. One of the most feasible hypotheses suggests that defects in the processes involved in the uptake of pigment precursors by specific tissues or their storage might explain that the pteridine and ommochrome pathways could be interrelated through common use or control of such processes. It is the long term goal of this proposed research to test this hypothesis by using an atypical eye-pigmented species of Drosophila. A variety of procedures and techniques, which include 2-eimensional thin layer chromatography and combination gas chromatography-mass spectrometry, will be employed to isolate, quantify, and identify the pteridines and ommochrome(s) present in D. acanthoptera. Additionally transmission electron microscopy will be done on the compound eyes and larval tissues to determine pigment movements, and enzyme activity profiles will be completed on major enzymes in the biosynthetic pathways of pteridines and ommochromes in D. acanthoptera. The eye screening pigmentation system provides a model system that could be applicable to the study of gene regulation in higher eukaryotes. Also by studying the eye pigmentation system we may be able to provide a greater understanding of the molecular mechanisms involved in tissue differentiation and cell specialization. In few other developmental systems is there such a range of mutants and natural occurring variation available in which the final phenotypes of the cells are altered, often in quantifiable ways.